Device-to-device (D2D) communication may be referred to as direct communication between two mobile devices without traversing a base station or core network (e.g., a cellular network). There are some situations in which a mobile device user may be outside of coverage areas of cellular communications. For example, a user may be hiking in the woods where there is no cellular coverage. As another example, cellular coverage may be lost in some areas, e.g., after a natural disaster. In such situations, it may be desirable for a mobile device, such as a smart phone, to communicate with other mobile devices in a D2D communication network. For example, in an emergency situation (e.g., an injury during hiking), a user may want to be able to send out emergency signals to people who are near. As another example, in a natural disaster (e.g., a hurricane), it may be advantageous to be able to send out messages to a large group of mobile device users in order to coordinate evacuation or rescue efforts. In some situations, D2D communication may be preferred even if there is cellular coverage. For example, in a sports stadium or in a mall, the cellular signals may be congested. A user may want to turn off cellular communication, and instead communicate with friends using D2D communication. Therefore, there is a need to improved methods of D2D communications.